I loved La Nouba so much that I've seen it 3 times! I saw it with my mom, dad, and sis. I then had to take DH (DBF at the time), and then we had to take his mom! I've never seen Mystere, so I can't compare the two. The only other Cirque show I've seen live is O.
Looking at Mystere's trailer, it looks like there may be a couple of similar acts to La Nouba (tightrope, trampoline). But I'm sure they are presented differently. La Nouba is a wonderful show with beautiful music. If you enjoyed Mystere, I definitely recommend going!